50' Contour Lines -Yuma County

This dataset represents 50 foot contour intervals for Yuma County, Arizona. The data were created by processing hillshade TIF files derived from the U.S. Geological Survey National Elevation Dataset. The processing produced ESRI formatted coverages for each county or part of a county. The U.S. Geological Survey has developed a National Elevation Dataset (NED). The NED is a seamless mosaic of best-available elevation data. The 7.5-minute elevation data for the conterminous United States are the primary initial source data. In addition to the availability of complete 7.5-minute data, efficient processing methods were developed to filter production artifacts in the existing data, convert to the NAD83 datum, edge-match, and fill slivers of missing data at quadrangle seams. One of the effects of the NED processing steps is a much-improved base of elevation data for calculating slope and hydrologic derivatives. The specifications for the NED 1 arc second and 1/3 arc second data are - Geographic coordinate system, Horizontal datum of NAD83, except for AK which is NAD27, Vertical datum of NAVD88, except for AK which is NAVD29, Z units of meters.本数据集涵盖亚利桑那州尤马县的50英尺等高距数据。该数据通过处理源自美国地质调查局（U.S. Geological Survey）国家高程数据集（National Elevation Dataset, NED）的晕渲TIFF（hillshade TIF）文件生成。经处理后，生成了适用于每个县或县内部分区域的Esri格式覆盖数据。 美国地质调查局已开发出国家高程数据集（NED），该数据集是最优可用高程数据的无缝镶嵌成果。美国本土的7.5分钟分辨率高程数据是其核心初始源数据。除完整的7.5分钟分辨率数据外，研发团队还开发了高效的处理流程，可用于过滤现有数据中的生产伪影、将数据转换至NAD83基准面、完成边缘匹配，并填补图幅接缝处缺失的细碎数据空隙。 国家高程数据集的处理流程带来的一项显著优势是，可获得精度大幅提升的高程基础数据，用于坡度与水文衍生参数的计算。NED 1角秒与1/3角秒分辨率数据的规范如下：采用地理坐标系，水平基准面为NAD83（阿拉斯加州除外，其水平基准面为NAD27）；垂直基准面为NAVD88（阿拉斯加州除外，其垂直基准面为NAVD29）；Z轴单位为米。